Utilizing an assembly line of track equipment, the project churns 24/7, replacing six miles of ties and railbed on four working lines.
One line, sometimes two at a time, have to be shut down.
Track supervisor James T. Brown took Eyewitness News reporter Tim Fleischer on a drive by, showing a heavy duty workload, balancing safety and efficiency between Melrose and Woodlawn.
Every time a train comes through, because of its close proximity, the workers have to stop. They hear the horns. The train is coming through and these workers have to stop working for their safety.
"That's why we have stop signs for our protection. And why we have an out of service track for our protect track. So when the train does come on the opposite track, we have a place to clear up at," said Brown.
This six mile stretch, cut through bed rock experiences, water drainage issues and has eroded concrete ties that were supposed to last more than 30 years.
"The first thing we needed to do was to fix those areas. It became clear as we fixed them that we were getting more deterioration than we anticipated so we had to expedite the work to fix that," said Howard Permut, Metro-North President.
But now where all three lines merge in Mott Haven, additional problems have been detected that must also be fixed.
Hoping to prevent a two mile bottle neck, a new commuter schedule will begin Monday.
"A very high percentage of trains will be leaving a minute or two different than they are now accustomed to," adds Permut.
While the six mile stretch is slated to be finished by Labor Day, they hope to finish the Mott Haven work by the end of fall.
Work that moves along side commuter lines that also must keep moving.
MORE ON THE TRACK WORK: http://mta.info/BronxROW/bronxrow_improvements.html
CHECK YOUR SCHEDULE: http://new.mta.info/mnr